The desirability of applying a lubricant to the coating of bullets to be fired from a rifle has been recognized in the art for some time. Much of the work has been concerned with bullet slugs comprising an alloy of lead, tin and antimony and entailed the use of a wax-like lubricant applied to the surface thereof. In these applications, the wax adhered to the rifle barrel during firing. Maintenance of cleanliness of the interior of the rifle barrel and freedom from fouling are important in maintaining accuracy of the rifle firing which cannot be achieved by use of wax-like lubricants.
Examples of the prior art of this categary known to me at the present time are as follows:
U.S. Pat. No. 2,547,548 to Turner discloses a machine for continuously conveying bullets through a preheating area where they are preheated prior to applying a lubricant, which is solid at ordinary temperatures, but is rendered liquid by said heat to the surface of the bullet where it forms a film thereon.
U.S. Pat. No. 2,728,260 to Mills discloses an apparatus where cartridges enclosed in containers are transported in a conveyor through a bath of heated grease which is solid at ordinary temperatures and raised out of the bath to produce a solidified lubricated uniform surface thereon.
U.S. Pat. No. 2,403,032 to Stevens and U.S. Pat. No. 3,967,526 to Leich both combine the process of die forming of lead alloy slugs to final dimensions while at the same time applying a grease type of lubricant to grooves in the surface of these slugs.
Each of the foregoing all four patents have the disadvantage of the wax adhering to the interior of the barrel of the rifle as mentioned above.
U.S. Pat. No. 3,431,612 to Darigo teaches the formation of a jacket of harder metal such as copper or copper alloy upon the surface of the lead slug to form a metal jacketed bullet by electro-deposition. Various other methods of applying metal jackets to produce a superior bullet are disclosed but none of them disclose any method of lubricating the bullet so formed.
Efforts have been made to utilize molybdenum disulphide (MoS.sub.2) as a bullet lubricating coating, particularly as disclosed by Vatsvog in U.S. Pat. No. 4,196,670. Molybdenum disulphide is a hard substance occurring in nature as an Ore of molybdenum, is quite hard and has high pressure lubricating qualities but is highly immiscible and insoluble in most reagents thereby making it impossible to apply it successfully as a coating to a metal surface by ordinary means. Vatsvog in his patent attempts to mix a dispersion of molybydenum disulphide in a synthetic resin dissolved in a volatile hydrocarbon and upon evaporation of the latter relies on the resin to cause the molybdenum disulphide to adhere to the bullet surface. I also have attempted to utilize various resins and adhesives to cause molybdenum disulphide to adhere to a bullet surface but found them all unsuccessful as not producing a uniform coating and not causing sufficient adherence to withstand the heat and pressure found inside a gun barrel. In each case this has caused the molybdenum disulphide to flake off and not provide the lubrication sought after. A stronger bond between the molybdenum disulphide and the bullet surface is required.
The fouling of the interior of the rifle barrel after only a relatively few shots and thus impairing the accuracy of the firing, as well as wear on the rifle barrel is a problem which has remained unsolved successfully until my invention described herein.